Bar screen device

ABSTRACT

The invention relates to a bar screen device ( 1, 1′, 1″ ), especially for treating fibrous suspensions in the paper industry. Said device comprises a plurality of bars ( 2, 2′, 2″, 2″ ) which are fixed to at least one reinforcing element ( 3, 3′, 3″, 3″ ) in such a way that they extend parallel at a pre-determined mutual distance which is defined by spacer elements ( 4*, 4*′, 4*″, 4*″ ), the mutual distance between the same defining the width of the slits in the bar screen device. The spacer elements ( 4*, 4*′, 4*″, 4*″ ) are also embodied as connecting elements ( 4, 4′, 4″, 4″ ), especially in order to avoid notch-induced resistance variations, and fix the bars ( 2, 2′, 2″, 2″ ) to the reinforcing elements ( 3, 3′, 3″, 3″ ) in such a way that they are distanced, in all three dimensions, in a positively and force locking manner, from the base of the bars to as close as possible to the neutral fibres of the bars ( 2, 2′; 2″, 2″ ) impinged upon. In this way, the bars can be fixed to the reinforcing elements without welding, and the separated, spatially positively locking connections between the bars ( 2, 2′, 2″, 2″ ) and the combined spacer and connecting elements ( 4*, 4*′, 4*″, 4*″ ), and between the combined spacer and connecting elements ( 4, 4′, 4″, 4″ ) and the reinforcing elements ( 3, 3′, 3″, 3″ ), are largely free of any notch effect, such that the component resistance remains unlimited.

The invention refers to a slotted hole screening device, in particularfor use in the treatment of fiber suspensions used in the paper industryand which includes the features as set forth in the preamble in claim 1.

In the prior German patent application 100 52 715.9 of Oct. 24, 2000 andnot pre-published, a plug-in type slotted hole screen assembly isproposed which comprises at least one reinforcement element and where aplurality of rods are fixed in parallel disposition at pre-determinedspaced distances by means of spacer elements. The spaced distance ofthese rods determines the slotted hole screen assembly. The rods in thisplug-in type of slotted screen together with the reinforcement element,which for example, is configured as a reinforcement ring or fixatingring or with the spacer element forms a positive connection. The spacerelements can also be designed as single separate elements or, they canbe collectively designed as a unitary spacer comb.

It has been shown that in this slotted hole screen assembly the direct,positive and non-positive connection of the rods with the reinforcementelements is associated with a reduced lifespan of the screening devicedue to the jags that are induced at the rods. In addition, thenecessarily tightly matched tolerances of the rods with thereinforcement elements require a higher cost of manufacturing andassembly. It has been shown that with this type of slotted screenassembly that the direct form-fitting and force-fitting connection ofthe rods with the reinforcing elements or the spacer elements cannegatively impact the life span of the slotted screen assembly due tothe induced jagging effects on the rods. The tightly matching tolerancesof the rods and the reinforcement elements thus require an additionalexpenditure in manufacturing and assembly.

Form EP 0 929 714 B1 a slotted hole screening device is known whereinthe parallel profile rods are embedded in slotted U-shaped reinforcementrings and are positively attached at their lower end by means of a localdeformation in the reinforcement ring. The plastic deformation producesa jag and reduces the capacity and/or the life of the profile rods.

From EP 0 417 408 B1 a slotted holed screen device is known whichcomprises profile rods having reinforcement rings with groove shapedrecesses. The bottom of the groove is wider in order to fit the crosssection of the complementary profile wire bottom in both a positive andnon-positive manner. Accordingly, a profile wire bottom, viewed in crosssection, must be formed which is wider with respect to the entire lengthof the profile wire, which leads to flow-mechanically unfavorableconditions.

In EP 0 499 154 B1 a screening device is described comprising the baseelements, namely, profile rods and reinforcing rings. The profile wiresare positively connected with the reinforcement rings by means of asnap-closure. The groove shaped recesses likewise induce indentationeffect in the reinforcing rings leading to component fatigue.

Object of the invention is to overcome these afore-stated drawbacks ofthe prior art, and to provide a slotted hole screening device where theconnection between the rods and the reinforcement rings are carried outsubstantially without a jag-producing weakening and which can beproduced in a flexible and cost-efficient manner.

In accordance with the invention, a slotted hole screening device isprovided having features as set forth in patent claim 1.

Further advantageous embodiments are set forth in claims 2 to 11.

In the slotted screening device according to the invention, a spacerelement is provided having an integrated connecting element, whichsubstantially fulfills three different objects. First, the connectingelement is utilized for adjustment of the predetermined slot width ofthe slotted screening device, wherein the connecting element restsflatly on each of the rod bottom flanks facing the connecting elementand thus are spaced relative to each other at a predetermined distance.Furthermore, the presence of the connecting element raises the stabilityof the rod, in that a positive connection as close as possible to theneutral fiber of the bending-stressed rod (loaded) is realized. In thatmanner, the bearing reaction is not placed into the zone of the higheststress, that is, either in the head of the rod or the bottom of therod—but shifted into a zone of the rod which is less prone to stress.Thirdly, the connecting element forms a positive and non-positive snapconnection between the combined spacer and connecting element and thereinforcing element, so that the reinforcing element will not exhibitany weakening jags in transverse direction and to minimize a prematurecollapse of that component. In addition, this ensures a flexible andcost efficient production.

In accordance with a further embodiment of the invention, the connectingelements that are positively linked with the rods form a positiveconnection with the reinforcement elements. This type of connectionensures a simple and cost-efficient assembly. By configuring the seat ofthe connecting elements always the same way, the need of a bearingsupport for reinforcement elements having different dimensions isreduced.

Preferably, for the formation of the positive connection, anannular-shaped recess or a tenon-shaped protrusion is provided at leaston a front surface facing the rod. In both cases, they are facing therod bottom flanks and may comprise symmetrical, such as for example acylinder, an ellipses as well as asymmetrical shapes of recesses orprotrusions. The same applies to complementary shaped recesses orprotrusions in the rod bottom flanks. Due to pressing the protrusion anda complementary recess, a positive connection is being formed, which isable to absorb forces from all three dimensions.

In order to maintain an as low as possible flow resistance in theslotted hole screening device and in order to avoid retention of fiberduring operation, the side of the connecting element facing the fibersuspension is configured in a flow-enhancing manner, for example it isrespectively rounded.

Furthermore, the surfaces of the connecting element facing thereinforcement element are progressively adapted to the contour of thereinforcement element.

In accordance with a further embodiment, the slotted hole screeningdevice is configured as a slotted hole screen cylinder or a slotted holescreen basket and the reinforcing element is configured as a reinforcingring for absorbing the radial stresses. Thus, the connecting elementaccording to the invention in co-operation with the rod bottom widthreliably determines width of the slot or slit in such a slotted holescreen cylinder and the force of the bearing pressure reaction happensclose to the neutral fiber of the rods.

In a simplification of production and reduction of assembly parts,several connecting elements can be bundled in the form of a continuousconnecting element chain, which itself can comprise also one or moreconnecting element segments.

The connecting elements may be attached in larger spacing on a thinconnection wire by means of a joint welding process, for example,resistance welding, in order to reduce the overall number of small partsand to exclude a source for error when incorporating single connectingelements having different thicknesses. Also, when segmenting the chain,a suitable chain length for assembly is realized.

Preferably, the reinforcement elements can be pre-fabricated as ringsand additionally secured by means of a positive connection through asnap closure. This allows a higher operational security when joining andmounting the reinforcement rings and results also in a biggerfully-automated production yield.

In an alternative embodiment of a slotted hole screening deviceaccording to the invention, the positive connection of combined spacerand connecting element and rod will be formed in situ, wherebyco-operating complementary parts at the rod and at the combined spacer-and connecting element are impressed directly at the site throughbending.

In summary, it is essential when laying-out the slotted screening deviceaccording to the invention that the rods can be positively secured inthree dimensions without limitation. This is essentially realized whenthe positive connection between the rods and the connecting elementscombined with the spacer elements is disposed in close proximity to theneutral fiber of each of the bending-stressed rods. Furthermore, thepositive connection of the rod and the combination spacer/connectingelement will be separated from the positive connection of the rod withthe reinforcing element whereby both are advantageously configured so asto make them as less prone to jagging impact as possible. In thismanner, the slotted screen device according to the invention is producedin a cost efficient manner and without material-union of the connectingelements and the rods, and to thereby avoid that joining welding stressimpacts upon the assembly components.

Preferred embodiments of the invention will be described hereinafterwith reference to the appended drawings. It is shown in:

FIG. 1 a perspective partial view for illustration of essentialcomponents of a first preferred embodiment of a screening deviceaccording to the invention;

FIG. 2 a perspective partial view of the screening device according toFIG. 1 without reinforcing element.

FIG. 3 a and FIG. 3 b respective illustrations of a single component ofexamples of connecting elements,

FIG. 4 a to FIG. 4 c, respective embodiments showing a schematic crosssectional view of assembly illustrations of a form-fitting connectionbetween connecting element and rod;

FIG. 5 a and FIG. 5 b, respective embodiments showing a schematiccross-sectional view of assembly illustrations of a form-fittingconnection between connecting element and rods as well as reinforcingelement;

FIG. 6 a perspective partial view of a further embodiment of a screeningdevice according to the invention;

FIGS. 7 a and 7 b schematic partial views to illustrate furtherembodiments of a screening device according to the invention.

Same or corresponding elements in the Figures are generally indicated bysame reference numerals. Embodiments and modifications thereof asdescribed in the figures are to be understood only as exemplary and inno way as limiting the scope of the invention.

FIG. 1 shows a schematic perspective view of an embodiment of thescreening device 1, for use in the treatment of fiber suspension in thepaper industry, in particular for sorting. The screening device 1comprises in longitudinal direction rods 2 extending in paralleldirection, whereby for purposes of illustration only a partial view of arod 2 is shown in FIG. 1. With the aid of a spacer element designated as4*, which is combined with a connecting element, the parallel rods 2 arespaced form each other, thereby forming screen slots between neighboringrods 2. Furthermore, the slotted screen device 1 comprises severalreinforcing elements that are oriented orthogonal to the longitudinaldirection of the rods 2 and regularly spaced spacer element 3 forabsorbing the static and dynamic stresses of the screening device 1. Fora better overview, FIG. 1 only shows a partial view of the reinforcingelement 3. The form-fitting and force-fitting connection of rods 2 withthe reinforcing elements 3 is realized by means of the connectingelement 4, which is spatially disposed in-between. The connectingelement 4 positions a protrusion (not seen here) within a complementaryrecess 5 in the rod bottom area 11, which forms the form-fittingconnection between the rods 2 and the connecting elements 4. Thestructural details of the embodiments for the form-fitting connectionare in particular shown in FIGS. 3 a and 3 b, as well as FIGS. 4 a, 4 band 4 c and are further described in that context.

The connection of the reinforcing elements 3 with the connectingelements 4 as shown in FIG. 1 is a form-fitting connection, wherein theT-shaped lead of the reinforcing element 3 is positioned within aT-shaped complementary shaped recess in connecting element 4. FIG. 2shows a sketch of a detail of the screening device according to theinvention without the reinforcing element 3, in order to show thecomplementary configuration of the recess without being obstructed bythe reinforcing element 3.

The recesses are not limited to T-shaped configuration; of course, theycan have a teardrop shape or can also be polygonal.

In accordance with FIGS. 3 a and 3 b, various embodiment of connectingelements 4 and 4′ are hereinafter shown and described.

The connecting element 4 in FIG. 3 a is shown here as a closerillustration of a single perspective view. The connecting element 4 asshown here is divided into a sector which is facing the area of the rodbottom and a further sector which faces the reinforcing element 3. Thesection of the rod bottom, in connection with the rod bottom width,forms the spacer function of the connecting element 4. Depending on thedesired screen width of the screen device 1, the thickness D of theconnecting element 4 can be selected from a variety of differentthicknesses or may be realized by machining the front surface 12 of theconnecting element 4. FIG. 3 a shows a cylindrical tenon configured as aprotrusion 8 and disposed in orthogonal position relative to front face12* and representing a partial element of the form-fitting connection.The spatial orientation of the tenon within the front face 12* isdefined as a point of the axis of symmetry of the connecting element 4and the height H, wherein the height H is defined as the distancebetween the start of the rod bottom and height level H of the neutralfiber of the weighted rods 2.

The region of the connecting elements 4, which is facing the reinforcingelements 3, has a width B, which is slightly smaller than the distancebetween two neighboring rods 2. In a further embodiment, the connectingelements 4 can also be configured as members of a chain of connectingelements 9. In that case, the originally single connecting element 4 isarranged evenly spaced and identically oriented on a wire 10 andpreferably connected by material union. As a result, the connectingelements 4 are spatially arranged and oriented thereby simplifying theassembly of the connecting elements 4 with the rods 2.

FIG. 3 b shows an alternative embodiment of a connecting element 4′.When shifting the T-shaped recess into the reinforcing element 3′, theconnecting element 4′ can consequently be made of a uniform thickness Dthroughout over front faces 12 and 12′. Since this embodiment has nodivision into sectors of different thicknesses, production of theconnecting elements is rendered simpler and more cost-efficient. Whenforming the chain 9′ of connecting elements, the connecting elements 4′are likewise uniformly spaced and identically oriented at the T-shapedarea of the form-fitting connection and attached to the wire 10′. Theconnecting element chain 9′ thus has comparably advantageous propertiesas the embodiment described in FIG. 3 a.

FIGS. 4 a and 4 c show cross sectional illustrations of the variousformfitting connections between rod 2 and the connecting element 4 in aslotted screening device according to the invention. FIG. 4 aillustrates the afore-described embodiment showing the passage-likehole-shaped recess 5 in rod bottom area 11 of rods 2. In a designcomplementary to the connecting elements, the cylindrical tenons areconfigured as protrusions 8 at the front face 12* of the connectingelements 4. The height of the cylindrical tenons 8 is necessarilysmaller than the rod bottom of rods 2 so that the space-generating frontfaces 12 and 12* and the rod bottom areas 11 can rest flatlythrereagainst.

FIG. 4 b shows a cross section of rod 2′ having a recess 5′, which isformed as a conical counter sink in the area of the rod bottom 11′. Thisrecess 5′ can be realized through a reshaping process. Preferably, therecess 5′ is being formed by a machining production process, for exampleusing a twist drill. The advantage of configuring recess 5′ in thismanner is the effect of fewer jags in the recess 5′ and thecorrespondingly greater life expectancy of the rods 2′. Thecomplementary configuration of the protrusions 8 of the connectingelements 4′ is formed as a blunt cone. In the sectional representationof FIG. 4 b, the conical protrusion 8′ is shown as a blunt triangle.Other embodiments of protrusions 8 and 8′ are not shown here in detailand the complementary recesses 5 and 5′ can be configured asdisc-shaped, prism-shaped to in other geometric shapes.

FIG. 4 c illustrates another variant of a form-fitting connection. Here,the protrusion 6 is now provided in the area of rod bottom 11 of rod 2″.The protrusion 6 can for example be formed by means of reshaping thearea of the rod bottom by means of a stamping process. The complementaryrecess 7 of the connecting element 4′″ is here configured asspace-generating ring element, which circumferentially receives theprotrusion 6 of rod 2.

FIGS. 5 a to 5 b show a schematic representation of the form-fittingco-operation between the connecting elements 4 and 4′ and thereinforcing elements 3 and 3′.

FIG. 5 a shows the effect of the form-fitting snap connection betweenthe connecting element 4 and one reinforcing element 3 of the slottedscreen device according to the invention as in FIG. 1. In the left-handside illustration, the reinforcing element 3 is positioned below theconnecting element 4 in such a manner that the lead of the reinforcingelement 13 projects into a T-shaped recess of the connecting element 4.During assembly, the lead of reinforcing element 13 is pressed into therecess, such that the elastically deformable flanks 14 and 15 of theconnecting element 4 yield in longitudinal direction of the rods 2. Assoon as the lead of the reinforcing element 13 is entirely receivedwithin the recess of the connecting lament 4, the flanks 14 and 15 ofthe connecting element 4 bounce back.

In FIG. 5 b, an alternative form-fitting snap connection between theconnecting element 4′ and a reinforcing element 3′ is shown.

In that embodiment, the elastic flanks 17 and 18 are formed in thereinforcement element 3′ and provided with the complementary connectingelement 4′ with the T-shaped lead 16. The principle of the form-fittingsnap-connection is analogous to the embodiment as shown in FIG. 5 a.

As shown in FIG. 6, the embodiment of the slotted screen device 1′ isschematically illustrated in a perspective view. A connecting elementchain 9′ is utilized having an operating mechanism of the form-fittingconnection between the connecting element 4′″ and rod 2″ in accordancewith FIG. 4 c, which does not comprise single elements but has acomb-like configuration.

The connecting element chain 9″ according to FIG. 6 can be assembled bymeans of a material union with a pipe, which serves as a receptacle forrods 2, and a tub-shaped flat wire utilized for receiving the connectingelements 3. The pipe-shaped area is prepared in a machining step withslot shaped uniformly spaced recesses corresponding to the width of therod bottom. The annular shaped recesses 7 of connecting element chain9″, encloses the protrusions 6 of rods 2″ (not seen here) for aform-fitting connection.

According to a preferred embodiment, the slotted screen device 1′ isconfigured as slotted screen cylinder. For the uptake of radial forcesacting from the screen interior toward the outside, the ring shapedreinforcing elements 3″ are inserted in circumferential direction intothe tub-shaped area of the connecting element chain 9″. The tub- orC-shaped receptacle of the connecting element chain 9″ together with thering-shaped reinforcing element 3″ makes a form-fitting connection,which functions without any snap closure mechanism as shown in FIGS. 5 aand 5 b. Additionally, by means of the tub-shaped configuration, adirected and flow mechanically efficient draining of the fibersuspensions during operation is realized.

FIGS. 7 a and 7 b show a further slotted screen device 1″ with acomb-like configuration of the connecting element chain 9′″. As comparedto FIG. 6, where a closed pipe-shaped area for receiving the rods 2′″ isused, here, a looped and slotted metal element is used to realize thespacing. This thin-walled metal element is materially interconnectedwith the rod-shaped reinforcing element 3′″. Subsequently, rods 2′″which are formed without recesses 5, 5′ or protrusions 6, are insertedinto the recess of the looped connecting element chains 9′″. By means ofa bending process, whereby the rods are located radially on the inside,the slot-shaped recesses are narrowed by the space-generating web areas.When selecting the suitable material for the metal element, the hardnessof the metal element preferably should be higher than the materialhardness of the rods, the space-generating web areas will substantiallyretain their shape at a steady diminishing bending radius, while theybecome evenly pressed into the rod bottom areas 11 of the rods 2′″ thusforming local recesses and protrusions at the rod bottom areas. Theformation of recesses and protrusions at the rods' bottom areas per seform the form-fitting connection of rod 2′″ and the connecting elementchain 9′″.

While not shown here in detail, combinations of the afore-describedembodiments of connecting elements 4 to 4′″ and various reinforcingelements 3 to 3′″ can be realized in a slotted screening device 1, 1′,1″, 1′″. The invention is thus not limited to the afore-described andexplained details of the slotted screen device 1 to 1″, but numerouschanges and modifications are possible which those skilled in the artwill know how to carry out and that are within the scope of theinvention. Of course the slotted screen device 1, 1′, 1″, 1′″ need notbe configured as a level slotted screen mat, but can for example beconfigured as a slotted screen cylinder or as an arc-shaped curvedslotted screen mat.

Slotted Screen Device Reference numeral list

-   1, 1′, 11′ entire slotted hole screen device-   2, 2′, 2″, 2′″ rod-   3, 3′, 3″, 3′″ reinforcing element-   4, 4′, 4″, 4′″, connecting element-   4*, 4*′, 4*″, 4*′″ distancing element-   5, 5′ recess of the rod-   6 protrusion of the rod-   7 recess of the connecting element-   8, 8′, 8″ Protrusion of the connecting element-   9, 9′, 9″, 9′″ connecting element chain-   10 wire-   11 rod bottom area-   12 front face of the connecting element-   13 lead of the reinforcing element-   14, 15 snap-closure of the connecting element-   16 lead of the connecting element-   17, 18 snap-closure of the reinforcing element-   D spacer-generating thickness of the connecting element 4, 4′, 4″,    4′″-   B width-   H height level of the neutral fiber of the rod 2, 2′, 2″, 2′″

1-11. (canceled)
 12. A slotted screen device for the treatment of fibersuspensions in the paper industry, which comprises: a plurality of fixedrods extending in parallel direction and mutually spaced at apre-determined distance, and a spacer assembly including one or morespacer elements and at least one connecting element, and at least onereinforcing element connected to the spacer assembly; wherein the spacerelements are associated with the rods for maintaining a slot width forthe screen device and wherein the rods are fixed in three-dimensionaldirections in form-fitting manner by the spacer assembly such that therods are spaced in direction close to a neutral zone of the rods understress, which stress is transmitted to the reinforcing elements.
 13. Theslotted screen device according to claim 12, wherein the connectingelements forms a form-fitting connection with the reinforcing elementsin orthogonal direction to a longitudinal dimension of the rods.
 14. Theslotted screen device according to claim 12, wherein each of apre-determined variable slot width is established in dependence on thewidth of the rod bottom area and the connecting elements.
 15. Theslotted screen device according to claim 12, wherein the rods areprovided with one of recesses or protrusions and wherein the connectingelements are configured with complementary shaped recesses orprotrusions at a front surface of the connecting elements that is facingthe rods for forming the form-fitting connection of the rod bottom area.16. The slotted screen device according to claim 15, wherein the outercontour of connecting element is configured in a flow-efficient shape.17. The slotted screen device according to claim 15, wherein the frontface of the connecting element facing the reinforcing element, isconformed to a profile of the reinforcing element without transition.18. The slotted screen device according to claim 12, wherein the slottedscreen device is configured as a rotation-symmetrical screen cylinderand the reinforcing element is configured as a reinforcing ring forabsorbing radial stress.
 19. The slotted screen device according toclaim 12, wherein the connecting elements are configured in the shape ofa unitary connecting element chain, which comprises one or moreconnecting elements.
 20. The slotted screen device according to claim19, wherein one of the connecting elements or the connecting elementchain is connected to at least one reinforcing element.
 21. The slottedscreen device according to claim 20, wherein the form-fitting connectionis configured as a snap-connection.
 22. The slotted screen deviceaccording to claim 12, wherein each spacer element is firmly connectedwith each of the corresponding reinforcing elements and wherein theconnecting elements that are in form-fitting connection with the rodsare fully formed when the fixed spacer elements that are connected withthe respective reinforcing element are suitably bent.
 23. A slottedscreen device for the treatment of fiber suspensions in the paperindustry, which comprises: a plurality of fixed parallel extending rods,said rods are spaced from each other to establish a slot width for thescreen device; one or more spacer elements arranged at the rods forspacing the rods at a pre-determined distance, said spacer elements arealso configured as connecting elements; and at least one reinforcingelement; wherein the spacer elements are bearing flat at correspondingbottom flanks of the rods and are spaced from a rod bottom area indirection to an unstressed zone of the rod under stress for fixing therods in three-dimensional directions in form-fitting manner, and whereinthe stress from the rods are transmitted to the reinforcing elements.24. A slotted screen device for the treatment of fiber suspensions inthe paper industry, which comprises: a plurality of fixed rods extendingin parallel direction and spaced at a pre-determined distance, and oneor more spacer elements associated with the rods for establishing a slotwidth for the screen device, and at least one reinforcing element, andwherein the spacer elements are configured as connecting elements forfixing the rods in three-dimensional directions in such form-fittingmanner so that the rods are spaced in direction close to a neutral zoneof the rods under stress, whereby a force is transmitted to thereinforcing element.
 25. The slotted screen device according to claim12, wherein each of a pre-determined variable slot width is determinedthrough the cooperation between the rods and the connecting elements.